Relay module for implant

ABSTRACT

An implementation provides a system that includes: a control module including a first antenna, the control module configured to generate a first radio frequency (RF) signal and transmit the first RF signal using the first antenna; an implantable lead module including a second antenna and at least one electrode configured to stimulate excitable tissue of a subject; and a relay module configured to receive the first RF signal; generate a second RF signal based on the first RF signal, the second RF signal encoding a stimulus waveform to be applied by the at least one electrodes of the implantable lead module to stimulate the excitable tissue of the subject; and transmit the second RF signal to the implantable lead module.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/983,355, filed May 18, 2018, now allowed, which is a continuation ofU.S. application Ser. No. 15/002,610, filed Jan. 21, 2016, now U.S. Pat.No. 9,974,965, issued May 22, 2018, which is a continuation of U.S.application Ser. No. 13/621,530, filed Sep. 17, 2012, now U.S. Pat. No.9,242,103, issued Jan. 26, 2016, which claims the benefit of U.S.Provisional Application No. 61/535,295, filed Sep. 15, 2011, the entirecontents of which are hereby incorporated by reference.

BACKGROUND

Active implanted stimulation devices have been utilized for applicationssuch as pacing, defibrillation, spinal and gastric stimulation. Suchdevices typically include wired electrodes on a lead module hardwired toan implanted pulse generator (IPG) that contains an internal batterythat can be recharged periodically with an inductive coil rechargingsystem.

SUMMARY

In one aspect, a system includes a control module including a firstantenna, the control module being configured to generate a first radiofrequency (RF) signal and transmit the first RF signal using the firstantenna; an implantable lead module including a second antenna and atleast one electrode configured to stimulate excitable tissue of asubject; and a relay module configured to: receive the first RF signal;generate a second RF signal based on the first RF signal with the secondRF signal encoding a stimulus waveform to be applied to the electrodesof the implantable lead module to stimulate excitable tissue of asubject; and transmit the second RF signal, wherein the implantable leadmodule is configured to receive the second RF signal using the secondantenna, generate the stimulus waveform from the received second RFsignal, and apply the stimulus waveform to the excitable tissue of thesubject.

Implementations of this and other aspects may include the followingfeatures: a control module which may include a programming interface toallow a user to adjust parameters of the stimulation waveform; a firstantenna of the control module which may include a dipole antenna, afolded dipole antenna, a microstrip antenna, or a phased array ofantennas.

The relay module may include: a receive antenna layer configured toreceive the first RF signal transmitted by the first antenna of thecontrol module; at least one dielectric insulating layer; and a transmitantenna layer separated from the receive antenna layer by the dielectricinsulating layer, the transmit antenna layer being configured totransmit the second RF signal to the second antenna of the implantablelead module, the second RF signal being generated based on the first RFsignal, and the second RF signal encoding a stimulus waveform to beapplied by the at least one electrode of the implantable lead module tostimulate the excitable tissue of the subject.

The receive antenna layer of the relay module may include one of: apatch antenna, or a dipole antenna. The receive antenna layer mayfurther include at least one quarter wavelength antenna. The transmitantenna layer of the relay module may include one of: a patch antenna,or a dipole antenna. The transmit antenna layer may further include atleast one quarter wavelength antenna.

The relay module may further include a flexible circuit, wherein theflexible circuit may include a rectifier and a capacitor, and whereinthe capacitor is coupled to the rectifier and configured to store acharge during an initial portion of the first RF signal. The flexiblecircuit may further include a counter configured to cause the flexiblecircuit to generate a trigger upon an end of the initial portion. Theflexible circuit may further include an oscillator, coupled to thecounter and configured to generate, upon the trigger, a carrier signal,and wherein the flexible circuit may modulate the carrier signal with astimulus waveform encoded in the first RF signal to generate the secondRF signal. The flexible circuit may be configured to generate the secondRF signal based on the stimulus waveform during a stimulation portion ofthe first RF signal, wherein the second RF signal has a correspondingcarrier frequency that is substantially identical to that of the firstRF signal. The flexible circuit may further include a power amplifierconfigured to amplify the second RF signal, and wherein the transmitantenna layer may be configured to transmit the amplified second RFsignal to the second antenna of the implantable lead module. The poweramplifier may be powered by the charge stored in the capacitor duringthe initial portion of the first RF signal. The oscillator may betriggered by an amplitude shift keying in the first RF signal.

The first RF signal and the second RF signal may have respective carrierfrequencies that may be within a range of about 800 MHz to about 6 GHz.The respective carrier frequencies of the first and second RF signalsmay be different.

The relay module may be placed exterior to the subject and the relaymodule may further include a battery. The relay module may besubcutaneously placed underneath the subject's skin. The relay modulemay be placed on the subject's skin. The relay module is placed on awearable item.

The relay module may further include a position sensor configured toread positional information of the relay module. The position sensorcomprises one of: a touch sensor, a gyroscope, or an accelerometer. Thecontrol module may be further configured to: receive the positionalinformation from multiple relay modules; and choose a particular relaymodule to transmit the second RF signal to the implantable lead module,based on the positional information received, wherein the particularrelay module chosen is better coupled to the implantable lead modulethan at least one other relay module.

In another aspect, a method of stimulating excitable tissue in a subjectby using a relay module includes: transmitting a first RF signal from afirst antenna on a control module; receiving, by the relay module, thefirst RF signal from the first antenna on the control module;generating, by the relay module, a second RF signal based on the firstRF signal, the second RF signal containing power and encoding a stimuluswaveform to be applied by the at least one electrodes of the implantablelead module to stimulate excitable tissue of the subject; transmitting,by the relay module, the second RF signal to an implantable lead module;receiving, by the implantable lead module the second RF signal;generating, by the implantable lead module the stimulation waveform; andapplying, through at least one electrode on the implantable lead module,the stimulation waveform to the excitable tissue.

Implementations of this and other aspects may further include rectifyingan initial portion of the first RF signal to provide energy to store acharge on the relay module; generating the second RF signal at an end ofthe initial portion; and amplifying the second RF signal by using thestored charge before transmitting the second RF signal.

The method may further include: generating the second RF signal based ona trigger caused by an amplitude shift keying in the first RF signal,the amplitude shift keying corresponding to the end of the initialportion of the first RF signal. The method may further include:generating the second RF signal based on a trigger caused by counting anumber of cycles during the initial portion of the first RF signal.

The second RF pulse may include a portion to provide energy to power theimplantable lead module. The method may further include: configuringpolarity of at least one electrode of the implantable lead module basedon a subsequent portion of the second RF signal that encodes polaritysetting information of the at least one electrode.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 shows an example of a wireless stimulation system including arelay module.

FIGS. 2A and 2B show example of a portable Microwave Field Stimulator(MFS) device.

FIG. 3 is a block diagram showing an example of implantable lead module.

FIGS. 4A-4C show examples of configurations of a relay module.

FIGS. 5A-5C show examples of configurations of a relay module with aflexible circuit.

FIG. 6 is a block diagram showing an example of a circuit, such as aflexible circuit, used on a relay module.

FIG. 7 is a block diagram showing another example of a circuit, such asa flexible circuit, used on the relay module.

FIG. 8 is a timing diagram showing examples of the first RF signalreceived at the relay module 130 and subsequent waveforms generated bythe flexible circuit.

FIG. 9 is a flow chart showing an example process in which the wirelessstimulation system selects a particular relay module.

FIG. 10 shows example of a configuration of the relay module with aposition sensor.

FIG. 11 illustrates an example workflow of a wireless stimulation systemwith the relay module of FIG. 10.

FIG. 12A-E show example placements of the relay module.

FIG. 13A-L show example placements of the relay module as a wearableitem.

FIG. 14A-14D show example configurations of a portable MFS device.

FIG. 15 depicts relay module in the configuration of a watch.

DETAILED DESCRIPTION

FIG. 1 shows an example of a wireless stimulation system including arelay module 130. The wireless stimulation system includes a controlmodule, such as a portable microwave field simulator (MFS) device 100,the relay module 130, and an implantable lead module 140, which may bean implantable neural stimulator. In the example shown in FIG. 1, thelead module 140 is implanted in a subject, such as a human patient, oran animal.

The portable MFS device 100 includes an antenna 110. Antenna 110 may beconfigured to transmit a first radio frequency (RF) signal thatpropagates to relay module 130. The first RF signal may have acharacteristic carrier frequency within a range from about 800 MHz toabout 6 GHz.

As shown by FIG. 1, the relay module 130 may be placed subcutaneouslyunder the skin of a subject. The first RF signal from antenna 110 maypropagate through body boundary 120 to reach relay module 130. Relaymodule 130 may also be placed outside body boundary, for example, on thepatent's skin topically. Relay module 130 may also be placed as awearable item, as will be discussed in further detail later.

Relay module 130 may include a receive antenna 131 and a transmitantenna 132. Receive (Rx) antenna 131 is configured to receive the RFsignal from antenna 110. The coupling between antenna 110 and Rx antenna131 may be inductive, radiative, or any combinations thereof. The Rxantenna 131 may be coupled to transmit (Tx) antenna 132 by a dielectricinsulating layer(s) and flexible circuits, as will be discussed infurther detail below. The Tx antenna 132 transmits a second RF signal toan implantable lead module 140. The second RF signal may be derivedfrom, or otherwise based on, the first RF signal and may or may not havethe same characteristic carrier frequency of the first RF signal, aswill be discussed in further detail below. A RF module 130 may use, forexample, a conditioning circuit in combination with a power amplifier toshape and enhance the second RF signal before transmitting the second RFsignal to implantable lead module 140, as will be discussed below infurther detail.

An implantable lead module 140 has been implanted inside the body of asubject. The subject can be a live human or animal. The implantable leadmodule 140 is a passive device without an onboard power source, such asa battery. An implantable lead module 140 includes an antenna 141configured to receive the second RF signal from antenna 132. Thecoupling between antenna 141 and Tx antenna 132 may be inductive,radiative, or any combinations thereof. The implantable lead module 140includes one or more electrodes placed in close proximity to anexcitable tissue, such as, for example, neural tissue. The second RFsignal may contain energy to power the lead module 140, and may encode astimulus waveform. The lead module 140 may generate the stimuluswaveform from the second RF signal, and apply the stimulus waveform tothe excitable tissue using the electrodes. Examples of the lead module140 are described in, for example, U.S. patent application Ser. No.13/584,618, filed on Aug. 13, 2012, the entire contents of which areincorporated herein by reference.

FIGS. 2A and 2B show examples of a portable Microwave Field Stimulator(MFS) device. A portable MFS device 100 may include a power system 201,a controller 202, a user interface (UI) 203, a feedback subsystem 204,and antenna 110. Examples of the MFS are described in, for example, U.S.patent application Ser. No. 13/584,618, filed on Aug. 13, 2012.

As illustrated by FIG. 2A, a power system 201 may include a battery, forexample, a rechargeable power source such as, for example, a lithium-ionbattery, a lithium polymer battery, etc. The power system 201 providespower to a portable MFS device 100.

The controller 202 can create the first RF signal to be transmitted fromthe antenna 110 to the relay module 130, which in turn may generate andtransmit the second RF signal to the antenna 141 on the implantable leadmodule 140. As shown in FIG. 2A, the controller 202 may include memory211, pulse generator 212, modulator 213, and amplifier 214.

Memory 211 may be local memory on board of the portable MFS device 100.Memory 211 may include any type of non-volatile memories, such as, forexample, EEPROM, flash memory, etc. Memory 211 may store stimulationparameter settings, such as for example, pulse amplitude, waveformshape, repetition frequency, pulse duration, etc. Based on the storedstimulation parameter settings, pulse generator 212 may generatestimulation waveforms. Modulator 213 may generate a carrier frequency,for example, within a range from about 600 MHz to about 6 GHz. Thestimulation waveforms generated by pulse generator 212 may modulate thecarrier frequency. The resulting modulated carrier frequency signal maybe amplified by amplifier 214 to generate the first RF signal to betransmitted by antenna 110.

The controller 202 may receive input from the UI 203 and the feedbacksubsystem 204. UI 203 may include a Bluetooth circuit board, or a USBinterface connector. UI 203 may include a programmer interface for auser, such as a manufacturer's representative, to adjust stimulationparameters, such as, for example, stimulation frequency, pulse width,power amplitude, duration of treatment, waveform shape, pre-programmedoptions and patient reminders. The programming interface can cause theselected settings to be stored on memory 211 of controller 202. Theselected settings are used to create, for example, the appropriatestimulation waveforms for driving the electrodes on implantable leadmodule 140.

Feedback subsystem 204 also may provide input to the controller 202 increating the first RF signal. The feedback may be based on measurementsof reflected power on antenna 110. The reflected power may indicate thecoupling between antenna 110 and surrounding medium, as will bediscussed in further detail in association with FIG. 10.

Antenna 110 may include a dipole antenna, a folded dipole antenna, apatch antenna, a microstrip antenna, or a phased array of antennas.Antenna 110 may be impedance matched to air to improve couplingefficiency with relay module 130. Antenna 110 can be located on the topof a flexible fixation housing that encloses the MFS circuitry connectedwith a low loss cable, or within the MFS enclosure, or remote from theMFS connected through a low loss cable.

FIG. 2A illustrates an implementation in which the antenna 110 is housedwithin the enclosure of the portable MFS device 100. The housingenclosure of portable MFS device 100 can be made of materials such asneoprene, or polyurethane, or other similar material with similardielectric properties.

In another example, shown in FIG. 2B, antenna 110 may be located on theoutside of the portable MFS device 100 within a separate encasement bywhich the MFS power is hardwired to the antenna by a low loss cable. Theantenna 110 can be located as far as three feet from the relay module130, or alternatively may be coupled directly to the skin in theproximity of the implanted lead module 140.

FIG. 3 is a block diagram showing an example of implantable lead module140. Implantable lead module 140 is a passive device without an activepower supply, such as a battery. Implantable lead module 140 may be animplantable neural stimulator. Implantable lead module 140 may includeantenna 141, power management circuitry 310, passive charge balancecircuitry 318, and electrodes 322.

Antenna 141 is configured to receive the second RF signal from antenna132 on relay module 130. The Antenna 141 may be embedded as a dipole, apatch, a microstrip, folded dipole, other antenna configuration. Thesecond RF signal may have a carrier frequency in the GHz range andcontain electrical energy for powering the wireless implantable leadmodule 140 and for providing stimulation pulses to electrodes ofimplantable lead module. Once received by the antenna 141, the second RFsignal is routed to power management circuitry 310 as the input signal.

Power management circuitry 310 is configured to rectify the input signaland convert it to a DC power source. For example, the power managementcircuitry 310 may include a diode rectification bridge and a capacitor.The rectification may utilize one or more full wave diode bridgerectifiers within the power management circuitry 310.

The DC power source provides power to the stimulation circuitry 311 andlead logic circuitry 313. Stimulation circuitry 311 may extract thestimulation waveforms from the received input signal. The stimulationwaveforms may be shaped by pulse shaping RC timer circuitry 312 and thenapplied to the electrodes 322. Passive charge balancing circuitry 318may balance charges applied at the electrodes. Lead logic circuitry 313may detect a portion of the input signal containing polarity settinginformation for each electrode of the electrode array 322. Thisinformation may be used to set the polarity of electrode interface 314controlling the polarity assignment of each electrode on electrodes 322.A particular electrode on the electrode array 322 may be implanted neartarget excitable tissue. The excitable tissue can be, for example, acardiac tissue, a neural tissue, etc.

FIGS. 4A-4C show examples of configurations of a relay module 130. Arelay module 130 may include encapsulation materials 400 and antennalayers 401, as shown by FIG. 4A. Encapsulation materials 400 may be anymaterial that encapsulates relay module 130, such as most plastics. Theantenna layers 401 may be encapsulated underneath encapsulation material400.

FIG. 4B shows a profile view of one example of a layered configurationfor the Rx antenna 131 and the Tx antenna 132. Rx 131 in FIG. 4B is apatch antenna formed by a layered structure of two conductor layers 404and one insulator layer 405 in between. The conductor layers 404 mayinclude any appropriate conducting metal, for example, copper, silver,etc. The insulator layer 405 may include insulating dielectricmaterials, such as, for example, porcelain, glass, and most plastics.

As discussed above, relay module 130 may be placed either in proximityof the tissue medium within a few millimeters or subcutaneously underthe skin of a subject, such as a human or an animal. If placed outsidethe subject's body, the Rx antenna 131 may be coupled to the air and maybe impedance-matched to the air. If placed subcutaneously, the Rxantenna 131 may still be coupled to the air since the skin layercovering the antenna is sufficiently thin, having minimal effect on thecoupling efficiency between the antenna 110 and Rx antenna 131 of therelay module 130. The separation of the two conductor layers 404 and theelectromagnetic properties of the insulator layer 405 may determine theresonant frequency of Rx antenna 131. Rx antenna 131 may generally be aquarter wavelength antenna at this resonant frequency.

The Tx antenna 132 in FIG. 4B is also a patch antenna formed by alayered structure of two conductor layers 404 and one insulator layer405 in between. Likewise, the separation of the two conductor layers 404and the electromagnetic properties of the insulator layer 405 maydetermine the resonant frequency of Tx antenna 132. Similarly, Txantenna 131 may also be a quarter wavelength antenna at this resonantfrequency. In contrast to the Rx antenna 131, which may be coupled tothe air, Tx antenna 132 may be coupled to the tissue, especially whenrelay module 130 is placed subcutaneously. Tx antenna 132 may then beimpedance matched to tissue to improve coupling efficiency whentransmitting the second RF signal to implantable lead module 140 insidethe subject's body. The transmitting metal layer may have a smallersurface area than the ground plane and may have a specific shape forimproved coupling with surrounding tissue (e.g., if placed topically onthe subject's skin). As illustrated, Tx antenna 132 in FIG. 4B isseparated by another insulator layer 405 from Rx antenna 131.

Generally, a patch antenna may include a conducting material layer thatserves as a conducting plane; a dielectric insulating plane the size ofthe conducting plane placed over the conducting layer; and anotherconducting layer, smaller than the ground plane, shaped in a desiredpattern. If two patch antennas are separated by another insulatingplane, as illustrated by FIG. 4B, the E-field of the transmit patchantenna does not interact with the E-field of the receive patch antennaon the other side of the relay module, when no edge-effects are present.

FIG. 4C shows a profile view of another configuration of Rx antenna 131and Tx antenna 132 configured as dipole antennas. In this configuration,the Rx antenna 131 is formed by the shape and contour of the surface ofone conductor layer 404 while the Tx antenna 132 is formed by the shapeand contour of another conductor layer 404. The two conductor layers areseparated by an insulator layer 405. The shape and contour of eachconductor layer may generally determine the corresponding resonantfrequency. In this configuration, the Rx antenna 131 and the Tx antennamay also be quarter-wavelength antennas at their respective resonantfrequencies.

In FIGS. 4B and 4C, the ground plane of the Tx antenna 132 may face awayfrom the active radiator of the antenna 110 and the transmitting surfaceof Tx antenna 132 may face towards tissue in order to improve theefficiency of the Tx antenna 132 in relaying energy to the antenna 141on implantable module 140. Additionally, Rx antenna 132 may have asurface area much larger than antenna 141 on the implantable module 140.For example, in certain embodiments, the Rx antenna 132 may have surfacearea of four square centimeters or above, while the antenna 141 withinthe implanted lead module may have a surface area less than one tenth ofa square centimeter. The Rx antenna 131 may thus capture a much largerportion of the flux of EM energy (for example, hundreds of times larger)and relay that energy to the antenna 141 through the relay module Txantenna 132. Although FIGS. 4B and 4C respectively show a patch-on-patchconfiguration and a dipole-on-dipole configuration, other arrangementsmay be implemented, such as, for example, a patch-on-dipole or adipole-on-patch configuration.

FIGS. 5A-5C show examples of configurations of a relay module 130 with aflexible circuit. The RF signal may be received by a Rx antenna 131 fromthe antenna 110. This received RF signal may be modulated and amplifiedvia circuitry on a flexible circuit within the relay module 130. Theflexible circuit may be implemented in a flexible circuit boardsubstrate that is easily bendable within the body or on the surface ofthe skin. These electronics may be isolated from the antenna groundplanes by a layer of insulation. A layer of conductive material mayprovide the interconnections to route the input signal from the Rxantenna 131 and send the conditioned and amplified signal out throughthe Tx antenna 132. This circuitry may include amplification andconditioning functions, as will be discussed in detail in associationwith FIGS. 6-8.

The flexible circuit may be placed relative to the Rx antenna 131 andthe Tx antenna 132. For example, FIGS. 5A and 5B respectively show thefront view and the profile view of a configuration in which the flexcircuit 506, along with the components, are placed on the side of theantenna layers. In another example, FIG. 5C shows the profile view ofanother configuration in which the flexible circuit 506 and the surfacemount (SMT) flexible circuit components 507 are placed in between theantenna layers. Additionally, although not shown, the flexible circuitmay also be placed on the top or bottom of the antenna layers.

The relay module 130 may operate in two modes, a relay mode and arepeater mode. In relay mode, the relay module 130 may not alter thestimulation portion of the received first RF signal when transmittingthe second RF signal to the implantable lead module 140. In the repeatermode, however, the relay module 130 may enhance the stimulation portionof the received first RF signal when transmitting the second RF signalto the implantable lead module 140.

FIG. 6 is a block diagram showing an example of a circuit, such as aflexible circuit, used on the relay module 130. In this mode, relaymodule 130 operates as an RF signal replicator to transmit the second RFsignal at the same carrier frequency as the stimulus portion of thereceived first RF signal from the portable MFS device 100.

The first RF signal transmitted from the portable MFS device 100contains two separate portions of encoded carrier waveforms. The firstRF signal is received by Rx antenna 131 on relay module 130. A chargingportion of the received first RF signal may contain a long (e.g., about1 ms or above) burst of pulses at a carrier frequency. This chargingportion may be the initial portion of a particular signal pattern to berepeated in the first RF signal. This charging portion is used to chargea power storage reservoir circuit including a capacitor 605 within therelay module 130. For example, the flexible circuit may contain arectifier 601 to generate a DC power supply by rectifying and smoothingthe initial portion of the received first RF signal. The DC power supplymay store charges in, for example, capacitor 605. The stored charge maythen be used to power subsequent operations of relay module 130. Thesesubsequent operations may include, for example, subsequent transmissionof the second RF signal that powers the electrodes on implantable leadmodule 140. Specifically, implantable lead module 140 is a passivedevice without a power supply. In contrast, some implementations of therelay module 130, however, may include a power source, such as arechargeable battery. Once the second RF signal is received at thepassive implantable lead module 140, it may be demodulated to providethe stimulation waveforms to be applied at the electrodes 322. Asdiscussed above in association with FIG. 3, in some implementations, thesecond RF signal may also contain polarity setting information to beapplied in assigning the polarity of each electrode of the electrodearray 322. Details are discussed in U.S. patent application Ser. No.13/584,618, filed on Aug. 13, 2012. Thus, by transmitting the second RFsignal, derived from or otherwise based on the first RF signaltransmitted from portable MFS device 100, relay module 130 of FIG. 6 canpower a passive lead module 140.

A stimulation portion of the received first RF signal encodes stimuluswaveforms. This stimulation portion may be the later portion of thesignal pattern being repeated in the first RF signal. The stimulationportion of the first RF signal will be conditioned by stimulusconditioning circuitry 602 before transmission to implantable leadmodule 140. The stimulus waveforms may contain short (e.g., about 0.5 msor shorter) bursts of pulses. A low-noise amplifier 603 detects thestimulation portion of the first RF signal from Rx antenna 131 and feedsthe stimulation portion to a high power amplifier 604. In oneimplementation, the first RF signal contains amplitude shift keying toindicate the end of the initial portion (for charging, e.g., capacitor605) and the start of the stimulation portion. The amplitude shiftkeying may cause the stimulus conditioning circuitry 602 to generate atrigger to allow DC power to be received from the stored charge incapacitor 605. In another implementation, the stimulus conditioningcircuit may include a counter that is set to expire upon apre-determined number of pulse wave cycles. When the counter counts thenumber of pulse cycles in the received first RF signal has reached thepre-determined threshold, the counter will expire and generate atrigger. Upon the trigger, stored charge in capacitor 605 may beharvested to power, for example, stimulus conditioning circuit 602,low-noise amplifier 603 and power amplifier 604. In either exampleimplementation, the output from the power amplifier 604 drives the Txantenna 132 to transmit the amplified stimulus waveform at the originalcarrier frequency to the implantable lead module 140. The stored chargecan be recharged by the next repetition of the initial portion in thefirst RF signal received from portable MFS device 100.

FIG. 7 is a block diagram showing another example of a circuit, such asa flexible circuit, used on the relay module 130. In this mode, relaymodule 130 acts as an active modulated pulse transmitter. The modulator600 can provide a carrier signal at a different frequency than thefrequency of the first RF signal received from the portable MFS device100. The first RF signal is received by the Rx antenna 131 coupled toair.

The first RF signal received from portable MFS device 100 by Rx antenna131 contains two separate portions of encoded carrier waveforms. Asdiscussed above, an initial portion of the first RF signal may contain along (e.g., about 1 ms or above) burst of pulses at a carrier frequency.This initial portion is used to charge a power storage reservoir circuitincluding a capacitor 605 within the relay module 130. For example, theflexible circuit may contain a rectifier 601 to generate a DC powersupply by rectifying and smoothing the initial portion of the first RFsignal. The DC power supply may store charges in, for example, capacitor605. The stored charge may then be used to power subsequent powersubsequent operations of relay module 130. These subsequent operationsmay include, for example, subsequent transmission of the second RFsignal that powers the electrodes on implantable lead module 140. Asdiscussed above, implantable lead module 140 is a passive device withouta power supply. In contrast, some implementations of the relay module130, however, may include a power source, such as a rechargeablebattery. Once the second RF signal is received at the passiveimplantable lead module 140, it may be demodulated to provide thestimulation waveforms to be applied at the electrodes 322. As discussedabove in association with FIG. 3, in some implementations, the second RFsignal may also contain polarity setting information to be applied inassigning the polarity of each electrode of electrodes 322. Details ofdiscussed in U.S. patent application Ser. No. 13/584,618, filed on Aug.13, 2012. Thus, by transmitting the second RF signal, derived from orotherwise based on the first RF signal transmitted from portable MFSdevice 100, relay module 130 of FIG. 7 can also power a passive leadmodule 140.

A stimulation portion of the first RF signal encodes stimulus waveforms.This stimulation portion may be a later portion in a pattern beingrepeated in the first RF signal. The simulations portion of the first RFsignal will be conditioned by stimulus conditioning circuitry 602 andfurther modulated by TX modulator 700 before transmission to implantablelead module 140. The stimulus waveforms contain short (e.g., about 0.5ms or shorter) bursts of pulses. In one implementation, the first RFsignal contains amplitude shift keying to indicate the end of theinitial portion (for charging, e.g., capacitor 605) and the start of thestimulation portion. The amplitude shift keying may cause the stimulusconditioning circuitry 602 to generate a trigger to allow DC power to bereceived from the stored charge in capacitor 605. In anotherimplementation, the stimulus conditioning circuit may include a counterthat is set to expire upon a pre-determined number of pulse wave cycles.When the counted number of pulse cycles in the received first RF signalhas reached the pre-determined threshold, the counter will expire andgenerate a trigger. Upon the trigger, stored charge in capacitor 605 maybe harvested to power, for example, Tx modulator 700 and power amplifier604. In either example implementation, the stimulus waveform is mixedwith a carrier frequency of Tx modulator, the result is fed to poweramplifier 604, and the output from the power amplifier 604 drives the Txantenna 132 to transmit the amplified stimulus waveform modulated at thecarrier frequency of Tx modulator 132 to the implantable lead module140. As discussed above, the stored charge can be recharged by the nextinstance of the initial portion of the first RF signal received fromportable MFS device 100.

In this mode, the carrier frequency of the first RF signal transmittedby the portable MFS device 100 can be decoupled from the carrierfrequency of the stimulus waveform transmitted by the relay module 130.As long as the two carrier frequencies are sufficiently apart and thepass band of antenna 141 on implantable lead module 140 is sufficientlyselective, the electrodes on the implantable lead module may only bedriven by the stimulus waveform transmitted from relay module 130.

FIG. 8 is a timing diagram showing examples of the first RF signalreceived at the relay module 130 and subsequent waveforms generated bythe flexible circuit. For example, in microwave relay mode (illustratedin FIG. 6), the charging portion 801 utilized for charge storage mayinclude a burst of pulses 1 millisecond or longer in pulse duration.Between each repetition of the charging portion of long bursts, a shortburst, with pulse durations of 500 microseconds or less, encodes thestimulus waveforms. This portion is the stimulation portion 802. In oneimplementation, after every 1000 cycles of the short bursts, the storedpower is recharged/replenished by the long bursts for pulse durations of1 millisecond or longer. The cyclic pattern is repeated as needed topower the amplification circuitry on board the relay antenna module sothat stimulus waveforms are sent to passive, implantable lead module140.

Multiple implantable lead modules 140 may be implanted inside asubject's body. Multiple relay modules 130 may be configured to relayenergy from a portable MFS device 100 to the implantable lead modules140.

FIG. 9 is a flow chart 900 showing an example process in which thewireless stimulation system chooses a particular relay module forrelaying energy to a particular implantable lead module 140.

Initially, a user may input stimulation parameters into the portable MFSdevice 100 (902). The stimulation parameters may include, for example,frequency, amplitude, pulse width, treatment duration, etc. Theseparameters may be entered into portable MFS device 100 through aprogrammer module, e.g., UI 203 (904). Afterwards, the portable MFSdevice 100 may send power to each relay module 130 (906). As discussedbelow in FIGS. 10 and 11, each relay module 130 may include positionsensors to provide positional information of the respective relay module130. Example position sensors may include radio-frequency identification(RFID) devices, touch sensors, gyroscopes, etc.

Subsequently, the portable MFS device 100 may read the positionalinformation generated by the position sensors at the respective relaymodule 130 (908). Based on the positional information collected,portable MFS device 100 may determine the relay module 130 bestpositioned to relay energy to power a particular implantable lead module140. The relay module best positioned to relay energy may be the relaymodule with one of the following characteristics: the lowest amount oftransmission loss, best coupling to tissue, closest proximity to theportable MFS device 100, or closest proximity to a particularimplantable lead module 140. For example, a software algorithm may beimplemented on the portable MFS device 100 to determine the position ofa particular relay module 130 relative to a given implanted implantablelead module 130. The portable MFS device 100 may then determine whichrelay module should be selected to transmit energy most efficiently tothe given implanted implantable lead module 130. In this example, therelay module that will transmit energy most efficiently to the givenimplantable lead module may be the relay module closest to the givenimplantable lead module. The portable MFS device 100 can digitallycontrol a multiplexor to selectively transmit energy to a chosen relaymodule 130.

Thereafter, the portable MFS device 100 may generate the first RF signalby modulating a carrier signal with a particular stimulation waveform,for example, according to stimulation parameters stored in memory 211(910). The portable MFS device 100 may then send the first RF signal tothe optimal relay module as determined above (911). The selected optimalrelay module may be the only relay module activated to receive the firstRF signal. The activation may be achieved remotely by portable MFSdevice 100 before transmission of the first RF signal.

When the selected optimal relay module receives the first RF signal atits Rx antenna 131, the relay module may utilize a charging portion ofthe received first RF signal to charge a reservoir, such as, forexample, capacitor 605, and then utilize the stored charge to power therelay circuitry (912). For example, the stored charge may be used tomodulate a carrier wave with a stimulation waveform, amplifier themodulated carrier wave to provide the second RF signal, and thentransmit the second RF signal to the given implantable lead module(914).

Subsequently, the given implantable lead module receives the second RFsignal. As a passive device, the given implantable lead module ispowered by the energy contained in the second RF signal and extracts thestimulation waveform from the received second RF signal (916). Incapturing the energy contained in the second RF signal, the implantablelead module 140 may store a charge in a capacitor. The stored chargewill be utilized to apply the extracted stimulation waveform to theelectrodes 322 (918).

FIG. 10 shows an example of a configuration of a relay module 130 with aposition sensor 1000. As illustrated, position sensor 1000 may beintegrated on flexible circuit 506. As shown in the left panel of FIG.10, the flexible circuit 506 may be placed on top of antenna layers 401and occupying part of the surface area of antenna layers 401.Encapsulation material 400 may enclose flexible circuit 506 (withcomponents) and antenna layers 401, as discussed above.

The right panel shows a profile view of the example configuration ofrelay module 130 with positional sensor 1000. Position sensor 1000 maybe a component of the surface mount (SMT) components 507 mounted onflexible circuit 506. As discussed above, the Rx antenna 131 and the Txantenna 132 may be implemented as patch-on-patch antennas. The Txantenna 132 of each relay module 130 can be circularly polarized tosubstantially obviate directional dependence, thereby permitting a wideracceptance angle at the antenna 141 on implantable lead module 140.

In one implementation, a semiconductor gyroscope can be used as aposition sensor to determine the orientation of Rx antenna 131 and Txantenna 132. In other implementations, touch sensors can be used as aposition sensor to detect, for example, if the Tx antenna 132 of therelay module 130 is coming in contact with an object. The touch sensormay also detect any force gradients to determine whether the side of Txantenna 132 is touching something pliable, such as clothing, orsomething hard. In particular, when Tx antenna 132 is touching a lossysurface, like the thigh, it could be considered a worst case scenario. Alossy surface may have different impedance than the impedance of theantenna. When the Rx antenna 131 or the Tx antenna 132 is touching aside pocket material, or other clothing, antenna coupling could becloser to that of air coupling, which may be considered the best-casescenario.

In yet other implementations, an additional coupler can be used todetect the forward power and reflection outputted by a given Tx antenna132. A lossy surface may be detected when the measured reflectionmeasurement is high, such as, for example, over 25% of the transmissionenergy. The presence of a lossy surface on a particular relay module mayprovide feedback to portable MFS device 100 that the particular relaymodule should be avoided. As a result, an alert may be provided to UI203 on portable MFS device 100 to notify a user of the situation. Unlessthe situation has been remedied, the portable MFS device 100 may refrainfrom using the given relay module to relay energy to an implantable leadmodule.

FIG. 11 illustrates an example workflow of a wireless stimulation systemwith the relay module 130 of FIG. 10. In step 1, the portable MFS device100 transmits omnidirectional charging signal to all relay modules inrange. In step 2, position sensors on the relay module 130 providepositional readings for the host relay module and utilize a telemetryantenna within the relay module to transmit the positional informationto the portable MFS device as a feedback signal from the positionsensors. In some implementations, Rx antenna 131 may serve as atransceiver to transmit the telemetry signal to the portable MFS device100. In these implementations, relay module 130 may include a powersource, such as, for example, a rechargeable battery. In step 3, theportable MFS device 100 receives the information from the positionsensors on the respective relay modules. Based on the positionalinformation received, the portable MFS device 100 software algorithmsdetermine which relay module 130 is in the most optimal position torelay the maximum amount of energy to power a given implantable leadmodule 140 that has already been implanted in the subject, as discussedabove. In step 4, portable MFS device 100 sends energy directed to thechosen relay module 130. Thereafter, the relay module 130 harvests theenergy to power the given implantable lead module 140, as discussedabove.

FIG. 12A-E show example placements of the relay module. The relay module130 can be placed nearby a variety of anatomical targets that containthe implanted lead module. Example targeted sites for relay module 130include, but are not limited to, behind the neck or at the small of theback as shown in FIG. 12A; the waistline or abdomen, as shown in FIG.12B; the side of the buttock as shown in FIG. 12C. The relay module 130may also be placed under the skin in the skullcap, as illustrated inFIG. 12D, and just under the skin over the vagus nerve around the neckarea, as illustrated in FIG. 12E.

FIGS. 13A-L show example placements of the relay module as a wearableitem. Relay module 130 may be placed, for example, a bandage, a strap,an adhesive surface, a sleeve cover, or a piece of cloth worn on thebody, for instance behind the neck or at the small of the back. FIG. 13Ashows an example placement of relay module 130 in an eyeglass frame1301. FIG. 13B depicts a dress shirt 1310 with relay modules 130attached to the inside and outside. FIG. 13C depicts relay module 130placed on the inside and outside of a general use shirt 1320. FIG. 13Ddepicts an example placement of relay module 130 in a neck brace orother stabilization brace 1330. FIG. 13E shows example placement ofrelay module 130 in a ball cap 1340. FIG. 13F shows example placement ofrelay module 130 PR on a flexible ace bandage 1350 housing which can beutilized at a multitude of locations on the body. FIG. 13G shows exampleplacement of relay module 130 on an ankle brace 1360. FIG. 13H d showsan example of placing relay module 130 within a girdle or haulter 1370.FIG. 13I shows example placement of relay module 130 on the body of abra structure 1380. FIG. 13J shows example placement of relay module 130on trunks 1390. FIG. 13K depicts example placement of relay module 130in multiple locations on a leg brace 1391. FIG. 13L depicts exampleplacement of relay module 130 within a scarf material 1392.

The design of the relay module 130 is intended to be convenient forpatient use in daily activities such as exercise, working, and otherleisure activities. A strap holding the relay module 130 over animplanted antenna 141 on implantable lead module 140 can becomeinconvenient in situations such as swimming, such as where the relaymodule 130 can shift, for example, during the sleeping time of thesubject; or where the relay module 130 could press against the skinpotentially uncomfortably. Additionally, bulky medical devices tend tobe unaesthetic and are undesirable in many situations where skin isexposed.

The implementations discussed above address these issues by placing thepulse generator on the portable MFS device 100 wirelessly away from thebody up to three feet. The implementations utilize a compact relaymodule 130 that may seamlessly integrate into a wearable item or besubcutaneously placed. The relay module 130 may relay energy receivedfrom portable MFS device 100 to power implantable lead module 140. Someimplementations may further detect which relay module is in contact withlossy materials and guides the pulsed microwave energy from portable MFSdevice 100 to be directed to the relay module with the best coupling toa particular implantable lead module.

FIG. 14A-14D show example configurations of a portable MFS device. Asdiscussed above, the portable MFS device 100 may be typically locatedoutside the body and is not physically connected to the skin; howevercan be located subcutaneously (not shown). In certain embodiments, aprogrammer is embedded into the portable MFS device 100 that interfaceswith a user to provide options to change the frequency, amplitude, pulsewidth, treatment duration, and other system specifications. In certaincircumstances, a manufacturer's representative will set specificparameters for the MFS device and the patient will be given the optionto adjust certain subsets of those parameters, within a specified range,based on a user's experience.

FIG. 14A shows an example portable MFS device 100 with a strap 1401,surface 1402, and control buttons 1403-1406 for a user to makeadjustments to the stimulation parameters. Antenna 110 may be mountedunder surface 1402. FIG. 14B shows another example portable MFS device100 with a display 1410 on surface 1402, and control buttons 1405 and1406. Antenna 110 may be mounted under surface 1402. The display 1410may provide visual information to a user about the progress of thetherapy and associated stimulation parameters. Control buttons 1405 and1406 may allow a user to make adjustments to the stimulation parameters.FIG. 14C shows yet another example portable MFS device 100 with asurface 1402, and control buttons 1403 to 1406. Antenna 110 may bemounted under surface 1402. Control buttons 1403-1406 may allow a userto make adjustments to the stimulation parameters. FIG. 14D shows stillanother example portable MFS device 100 with antenna 110 and controlbuttons 1403-1406 for a user to make adjustments to the stimulationparameters.

FIG. 15 depicts the MFS and Tx antenna in the configuration of a watchor other strap on arm unit. In certain embodiments, the Tx antenna islocated on the perimeter of the watch face, or optionally on the strapof the watch or arm unit.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherimplementations are within the scope of the following claims.

What is claimed is:
 1. A system comprising a wirelessly powered relaydevice, wherein the wirelessly powered relay device comprising: areceiver antenna layer configured to receive a first radio-frequency(RF) signal transmitted by a first antenna of a control device, whereinthe first RF signal contains electrical energy; at least one dielectricinsulating layer; and a transmitter antenna layer separated from thereceiver antenna layer by the dielectric insulating layer, wherein thetransmitter antenna layer is configured to transmit a second RF signal,and the second RF signal is generated using the electrical energycontained in the first RF signal.
 2. The system of claim 1, wherein thereceiver antenna layer of the wirelessly powered relay device furthercomprises one of: a patch antenna, or a dipole antenna, wherein thetransmitter antenna layer of the wirelessly powered relay device furthercomprises one of: a patch antenna, or a dipole antenna.
 3. The system ofclaim 1, wherein the wirelessly powered relay device further comprises aflexible circuit, wherein the flexible circuit comprises a rectifier anda capacitor, and wherein the capacitor is coupled to the rectifier andconfigured to store a charge during an initial portion of the first RFsignal.
 4. The system of claim 3, wherein the flexible circuit furthercomprises a counter configured to cause the flexible circuit to generatea trigger upon an end of the initial portion.
 5. The system of claim 4,wherein the flexible circuit further comprises an oscillator, coupled tothe counter and configured to generate, upon the trigger, a carriersignal, and wherein the flexible circuit modulates the carrier signalwith a stimulus waveform encoded in the first RF signal to generate thesecond RF signal.
 6. The system of claim 5, wherein the flexible circuitis configured to generate the second RF signal based on the stimuluswaveform during a stimulation portion of the first RF signal, whereinthe second RF signal has a corresponding carrier frequency that issubstantially identical to that of the first RF signal.
 7. The system ofclaim 5, wherein the flexible circuit further comprises a poweramplifier configured to amplify the second RF signal solely usingcharges accumulated in the capacitor during the initial portion of thefirst RF signal, and wherein the transmitter antenna layer is configuredto transmit the amplified second RF signal via non-inductive coupling toa second antenna on an implantable stimulator device.
 8. The system ofclaim 7, wherein the power amplifier is configurable to be powered bythe charge stored in the capacitor during the initial portion of thefirst RF signal.
 9. The system of claim 5, wherein the oscillator isconfigurable to be triggered by an amplitude shift keying in the firstRF signal.
 10. The system of claim 1, wherein the receiver antenna layercomprises at least one quarter wavelength antenna, wherein thetransmitter antenna layer comprises at least one quarter wavelengthantenna.
 11. The system of claim 1, wherein the wirelessly powered relaydevice is configured to generate the second RF signal during astimulation portion of the first RF signal and by using a chargeaccumulated on the wirelessly powered relay device during an initialportion of the first RF signal, wherein the initial portion precedes thestimulation portion, and wherein the second RF signal encodes a stimuluswaveform.
 12. The system of claim 1, wherein the wirelessly poweredrelay device is sized and shaped to be placed outside a subjectreceiving an implantable stimulator device.
 13. The system of claim 12,further comprising: an implantable stimulator device comprising a secondantenna and at least one electrode, wherein the implantable stimulatordevice is configured to receive the second RF signal using the secondantenna, extract a stimulus waveform from the received second RF signal,and apply the stimulus waveform to a neural tissue of the subject usingthe at least one electrode.
 14. The system of claim 1, furthercomprising: a control device comprising the first antenna, wherein thecontrol device is configured to generate the RF signal and transmit thefirst RF signal using the first antenna.
 15. The system of claim 14,wherein the control device further comprises a programming interface toallow a user to adjust parameters of a stimulus waveform.
 16. The systemof claim 14, wherein the first antenna of the control device comprisesone of: a dipole antenna, folded dipole antenna, microstrip antenna, ora phased array of antennas.
 17. The system of claim 14, wherein thecontrol device is configured to transmit the first RF signal at a firstcarrier frequency, and wherein the wirelessly powered relay device isconfigured to transmit the second RF signal at a second carrierfrequency, and wherein both the first carrier frequency and the secondcarrier frequency are within a range of about 800 MHz to about 6 GHz.18. The system of claim 17, wherein the first carrier frequency and thesecond carrier frequency are configurable to differ from each other. 19.A system, comprising: a control module comprising a first antenna, thecontrol module configured to generate a first radio frequency (RF)signal and transmit the first RF signal using the first antenna, animplantable lead module comprising a second antenna and at least oneelectrode, the at least one electrode being configured to stimulate anexcitable tissue of a subject; and a relay module configured to: receivethe first RF signal; generate a second RF signal based on the first RFsignal, the second RF signal encoding a stimulus waveform to be appliedby the at least one electrode of the implantable lead module tostimulate the excitable tissue of the subject; and transmit the secondRF signal, wherein the relay module comprises: a receive antenna layerconfigured to receive the first RF signal transmitted by the firstantenna of the control module; at least one dielectric insulation layer;and a transmit antenna layer separated from the receive antenna layer bythe dielectric insulating layer, the transmit antenna layer beingconfigured to transmit the second RF signal to the second antenna of theimplantable lead module, the second RF signal being generated based onthe first RF signal, and the second RF signal encoding a stimuluswaveform being applied by the at least one electrode of the implantablelead module to stimulate the excitable tissue of the subject, whereinthe implantable lead module is configured to receive the second RFsignal using the second antenna, generate the stimulus waveform from thereceived second RF signal, and apply the stimulus waveform to theexcitable tissue of the subject.
 20. The system of claim 19, wherein thecontrol module further comprises: a programming interface to allow auser to adjust parameters of the stimulus waveform.